This invention relates to a material activator for a material dispensing bin and more particularly to an activator for preventing material bridging which could interrupt flow of material through the bin outlet.
Bins, hoppers, chutes, and the like have been employed for dispensing materials. Each of these container types has an outlet through which the material is dispensed and usually has some form of gate or valve mechanism at the outlet to stop flow of dispensed material from the container through the outlet. Dry materials in the form of powders, aggregates, granular, fines, chopped or ground materials including recycle plastics and the like when dispensed through various types of containers can cause hang up or bridging of the material above the bin outlet. The extent of bridging, hang up, and compaction of the material varies depending, for example, upon the physical characteristics of the material, electrostatic attraction of the materials and the degree of dryness.
Various techniques have been implemented to avoid material bridging. Such devices can be categorized into at least two principle areas: vibratory and mechanical. Examples of vibratory devices are described in Canadian Patent No. 1,178,934 and U.S. Pat. No. 3,715,059. The vibratory devices may be mounted on either the inside or outside of the bin wall and produce vibration in the neck area of the bin to prevent material hang up and/or bridging. However, vibratory devices, should bridging occur, can actually increase the compaction in the bridged material.
Mechanical systems involve moving devices which directly contact the material, for example, as shown in U.S. Pat. No. 4,176,767, a manually operated spring device may be pushed up into the bin outlet to break up any bridging of the material. Canadian Patent No. 1,048,457 describes scrapers which are pivotally mounted on the bin side wall and are moved up and down by lugs on a endless conveyor to prevent bridging on the tapered portions of the bin. U.S. Pat. Nos. 3,804,304 and 5,277,337 describe rotary scraper devices mounted near the tapered outlet of the bin to move the material around and physically break up any bridging action in the moving material.
Movement of material from a dispensing bin becomes particularly important when combining predetermined amounts of dispensed materials to form a batch for subsequent processing. Any hang up in any one of the material dispensing devices can greatly delay the production of the batch. This is particularly prevalent when blending plastic resins for injection molding systems. Furthermore, if the amount of the material to be dispensed is based on time it is critical that the material always flow out of the outlet at a desired flow rate so that the correct amount is metered for each batch. This may become an issue when blending plastic resins for injection molding systems. It may be that four or more different types of plastics are to be metered and dispensed. Some of these plastics may have electrostatic properties which can encourage the formation of bridges in the bin. This is particularly true with ground recycled plastic such as recycled PET (polyethylene teraphthalate).
Although it is appreciated that similar significant problems exist in dispensing fine powders such as grain flour, there continues to be a need for a compact style of material activator which is readily installed as original equipment or may be retro-fitted on existing equipment.
In accordance with an aspect of this invention, a material activator is provided for a dispensing container such as a bin, hopper, chute and the like. The activator is positioned on the bin inside wall in the tapered area of the bin where bridging naturally occurs. The activator comprises a movable slide which reciprocates along the inside wall to break up any material bridging or hang up. The actuation of the slide may be based on a timed event, a bridge sensing device, or a flow sensor.
According to an aspect of the invention, provided is a material activator device for use in maintaining material flow from a material dispenser, said device comprising:
i) a mount for mounting said device to said material dispenser;
ii) a reciprocal slide for movement through the region in which material blockage is likely to occur; and
iii) an actuator having a reciprocal piston rod connected to said slide.
According to another aspect of the invention, provided is a method of maintaining material flow in a material dispenser, said method comprising reciprocating a slide through the material in the region in which material blockage is most likely to occur to thereby prevent material blockage and maintain material flow.